The Esp8266 runs on 3.3v, if the pin 11 on the arduino is not passed through a level shifter or brought down to 3.3 with a resistors it can cause the board to malfunction.

As the Ardnuino Uno takes male jumper cables while the ESP 8266 requires female jumper cables, a bread board can be used to make the connections. Its also useful as both the CH_PD and VCC pins on the ESP 8266 require power.